This document discusses different types of looping control structures in C++ programming, including for, while, and do-while loops. It provides the syntax for each loop and examples of how they work. The key points are: - Loops allow repeating execution of a block of code multiple times. - C++ has three main types of loops: for, while, and do-while. - For loops iterate a specific number of times as defined by the initialization, condition, and increment/decrement statements. - While loops continuously execute while a condition is true. - Do-while loops execute the body at least once even if the condition is false, since the condition is checked at the bottom.

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Unit-1
Principles of Object Oriented Programming Tokens,
expressions & Control Statements
(14 MARKS)
B.C.A & B.Sc.(IT) – 3
CS-13 C++ and Object Oriented
Programming

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Looping Control
Structure

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• There may be a situation, when you need to execute a
block of code several number of times.
• In general, statements are executed sequentially: The
first statement in a function is executed first, followed
by the second, and so on.
• Programming languages provide various control
structures that allow for more complicated execution
paths.

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• A loop statement allows us to execute a statement or
group of statements multiple times and following is
the general from of a loop statement in most of the
programming languages −

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• C++ programming language provides the following
type of loops to handle looping requirements.
1. for,
2. while,
3. do… while

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For Loop
•A for loop is a repetition control structure that
allows you to efficiently write a loop that needs
to execute a specific number of times.

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Syntax
The syntax of a for loop in C++ is −
for ( init; condition; increment/decrement )
{
statement(s);
}

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• Here is the flow of control in a for loop −
• The init step is executed first, and only once.
• This step allows you to declare and initialize any loop
control variables.
• Require semicolon (;).

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•Next, the condition is evaluated.
•If it is true, the body of the loop is executed.
•If it is false, the body of the loop does not execute
and flow of control jumps to the next statement
just after the for loop.

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•After the body of the for loop executes, the flow
of control jumps back up to
the increment statement.

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•The condition is now evaluated again.
•If it is true, the loop executes and the process
repeats itself (body of loop, then increment step,
and then again condition).
•After the condition becomes false, the for loop
terminates.

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Let’s see Examples: 7_For.cpp
7_forloop
Process

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• First initialize the variable
• In second step check condition
• In third step control goes inside loop body and
execute.
• At last increase the value of variable
• Same process is repeat until condition not false.

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While loop
• In while loop first check the condition if condition is
true then control goes inside the loop body
• Otherwise goes outside of the body. while loop will be
repeats in clock wise direction.

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Syntax
• The syntax of a while loop in C++ is -
while(condition)
{
statement(s);
}

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C++

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Let’s look at the Example: 9_whileDemo.cpp
9_while.cpp
9_whileLoop.cpp

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Do...while loop
• The only difference between While loop and do-while
loop is do-while loop at least execute one time.
• No matter if the condition is true or false.
• This happen because the condition of the loop is at
the bottom of body of the loop so, it will execute the
body at least once.

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Syntax
do
{
statement(s);
}
while( condition );

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• If the condition is true, the flow of control jumps back
up to do, and the statement(s) in the loop execute
again.
• This process repeats until the given condition becomes
false.

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Example: do_while.cpp
Example: dowhile.cpp

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• A loop becomes infinite loop if a condition never
becomes false.
• The for loop is traditionally used for this purpose.
• Since none of the three expressions that form the ‘for’
loop are required, you can make an endless loop by
leaving the conditional expression empty.
Infinite

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Example: 6_infinite.cpp
#include <iostream>
using namespace std;
int main ()
{
for( ; ; )
{
printf("This loop will run forever.n");
}
return 0; }

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• When the conditional expression is absent, it is
assumed to be true.
• You may have an initialization and increment
expression, but C++ programmers more commonly use
the ‘for (;;)’ construct to signify an infinite loop.
• NOTE − You can terminate an infinite loop by pressing
Ctrl + C keys.